Abiotic degradation of field wheat straw as a notable source of atmospheric carbonyls in the North China Plain.

Carbonyl compounds (carbonyls) play a crucial role in atmospheric chemistry, but their atmospheric sources are not fully identified. Here we show unexpectedly high carbonyl emissions from extensive field returning wheat straw over the North China Plain (NCP). The emission rates of carbonyls exhibit distinct diurnal variations with the noontime peak value of total carbonyls greater than 135 μg∙kg-1 (dry straw weight) ∙h-1. The carbonyl emission is mainly attributed to biomass abiotic degradation processes that are affected by air temperature and sunlight intensity. Given that the photolysis of carbonyls is the major primary source of ROx radicals in the troposphere, carbonyl emissions would lead to increasing atmospheric oxidants. The mean daytime O3 concentration over the NCP increases by 12.3% when coupling carbonyl emissions from wheat straw with the current emission inventory through the model simulation. It might be one of the important reasons for the occurrence of the most serious O3 pollution in June when winter wheat is intensively harvested in the region. Further studies are warranted to explore the influence of field returning wheat straw on regional air quality.